1. Technical Field
The present invention generally relates to an optical component; and more particularly to a tunable optical filter for filtering an optical signal using compression based tuning.
2. Description of Related Art
Bragg gratings have been utilized in a variety of applications that require a tunable optical filter. These filtering devices are inherently sensitive to both the applied strain and temperature, both of which have been used successfully to precisely tune the filters. The large diameter optical waveguide or cane-based tunable device provides a high level of grating control by enabling precise grating tunability through compression tuning while maintaining high reliability in the overall device. One important feature of the cane-based tunable grating is its ability to tune over an extended region compared to a fiber technique.
However, in such devices, the tuning range is limited and is set by the buckling strength of the grating region. A simple range extending technique could be to simply thicken the grating region; however, this requires more force to be placed on the device to achieve the same wavelength shift. If one looks at a device required to tune a typical 50 Gigahertz (GHz) grating over the entire C-Band (40 nanometer (nm)). A 7 millimeter (mm) long grating will buckle at about 500 lbs of applied force in the above configuration if the center diameter is 1.1 mm; this 500 lbs will also give the required 40 nm tuning range. Since in this example the element will break once it reaches the full tuning range, an additional safety factor needs to be applied, typically greater than 2. One can then see that the forces required to produce this device are unreasonable.
There is a need in the industry to provide a tunable optical filter using a Bragg grating that overcomes this problem.